Method of reacting pentaborane (11) with an acetylenic compound



United States Patent 3,293,303 METHOD OF REACTIN G PENTABORANEQI) WITH AN ACIETYLENIC CUMPOUND Emil A. Lawton, Columbus, and Arthur Levy, Worthington, Ohio, assignors, by mesne assignments, to The Battelle Development Corporation, Columbus, Ohio, a corporation of Delaware No Drawing. Filed June 25, 1956, Ser. No. 593,773 3 Claims. (Cl. 260-6065) This invention relates to fuels and, more particularly, to solid organoboron fuels.

The fuels of this invention, when incorporated with suitable oxidizers such as ammonium perchlorate, potas sium perchlorate, sodium perchlorate, ammonium nitrate, etc., yield solid propellants suitable for rocket power plants and other jet propelled devices. Such propellants burn with high flame speeds, have high heats of combustion and are of the high specific impulse type. Probably the single most important factor in determining the performance of a propellant charge is the specific impulse; appreciable increases in performance will result from the use of higher specific impulse materials. The fuels of this invention when incorporated with oxidizers are capable of being formed into a wide variety of grains, tablets, and shapes, all with desirable mechanical and chemical properties. Propellants produced by the methods described in this application burn uniformly without disintegration when ignited by conventional means, such as a prrotechnic type igniter, and are mechanically strong enough to withstand ordinary handling.

According to this invention, solid addition products of pentaborane(11) and acetylene hydrocarbons containing from 2 to 8 carbon atoms are prepared by the direct reaction of the pentaborane(11) and the hydrocarbon. The reaction temperature can be varied widely, generally being from about -25 C. to +50 C., and preferably from C. to 25 C. In like manner, the quantity of acetylene hydrocarbon utilized in the reaction can be varied over a wide range, from about 0.5 to 5 moles of acetylene hydrocarbon to 1 mole of pentaborane(11) generally being used.

The reaction time usually varies from 1 to 30 hours or more.

The pentaborane(11) starting material can be either pure pentaborane fll), B I-I or can be a mixture of B 11 with B H containing at least 70 mole percent of B H A mixture of 8 1-1 and B H containing 80 percent of the former can be prepared easily by pyrolysis of diborane at an elevated temperature of about 100130 C. This method is described in an article by A. B. Burg and H. I. Schlesinger, I. Am. Chem. Soc., 55, 4009 (1933). The pyrolysis products of this reaction are B H B H 3 H and B 11 plus minor amounts of nonvolatile boron hydrides. The B -H B H and non-volatile products are easily separated from the mixture of B H and B H Since there is little difference in the vapor pressure of B H and B H these compounds are not readily separated by fractionation. However, it was found that B H does not interfere with the reaction according to the present invention. The pentaborane starting material used in this reaction, according to the present invention, can contain, for example, from 10 to 20 percent by volume of B 11 and the balance B H although, of course, the pure B 11 can also be employed as a starting material.

Example I A mixture of 10.1 cc. of isoprope-nyl acetylene and 16.4 cc. of pentaboranefl 1) (of about 85 percent purity by volume, the remainder being pentaborane-9) both measured at S.T.P., were condensed into a small 10 cc. glass reactor 3,293,303 Patented Dec. 20, 1966 "ice tube which was maintained at a temperature of 196 C. The isopropenyl acetylene and pentaborane(11) were allowed to warm up to 17 C. and then cooled to 0 C. The initial pressure of the reaction system at 0 C. was 107 mm. of Hg. After 16 hours the pressure was mm. of Hg and at 21 hours the pressure was 79 mm. of Hg. At the end of 21 hours the reaction mixture was cooled to 80 C. and a vacuum applied to the reactor. The noncondensible gases were pumped off and removed from the system through the trap maintained at --196 C. The condensible gases retained in the trap held at 196 C. were allowed to warm up and were transferred to the original reactor which was also cooled to 196 C. during this operation. The reactor was again allowed to warm up to room temperature and the gases evolved were pumped off through a trap maintained at 196 C. as carried out before. During this operation a total of 13.3 cc. of condensible gases, measured under S.T.P. conditions, was retained in the trap cooled to -196 C. The reactor was then closed off and allowed to remain overnight at a temperature of approximately 20 C. C-ondensible gases were then removed from the reaction mixture by subjecting it to a vacuum and pumping off the gases evolved thrOugh a second trap at 196 C.; 0.9 cc. of condensible gas, measured at S.T.P., was retained in this trap. The condensible gases thus obtained (0.9 cc.) were allowed to warm up to room temperature and were transferred to the trap maintained at 196 C. which contained the 13.3 cc. of condensible gas previously trapped. Next, the reaction tube was sealed off and it was determined by weighing that 36.7 milligrams of product, a yellow wax-like solid, had been produced. By chemical analysis it was shown that the solid contained 17.0 percent boron and 36.0 millimoles of hydrolyzable hydrogen per gram of sample.

Example II Divinylacetylene (10.6 cc. 0.473 mmole) was condensed with B H (48.3 cc., of 2.15 mmoles) at 196 C. into a reaction vessel of approximately 40 cc. volume. The B H contained about percent by volume B l-l the remainder being pentaborane-9. The mixture was allowed to warm up to ambient temperature and then was set at 0 C. for a period of 17 hours. The pressure exerted by the mixture at 0 C. was initially 312 mm. of Hg and increased to 489 mm. of Hg after 17 hours. The volatile fraction was collected in a 196 C. trap, leaving behind a light yellow powder Weighing 67.2 mg.

A 27.8 mg. sample of the product was hydrolyzed and analyzed for boron content; analysis: 35.4 weight percent boron and 21 cc. hydrolyzable hydrogen (33.7 mmoles H per gram of sample).

Carbon and total hydrogen analysis were obtained on a 9.4 mg. aliquot of the reaction product; analysis: 41.9 weight percent carbon, 10.0 weight percent hydrogen.

In a similar manner, other solid organoboron fuels can be prepared in accordance with this invention by substituting other acetylene hydrocarbons containing from 2 to 8 carbon atoms for the isopropenyl acetylene and divinyl acetylene utilized in the examples. Thus, Table I sets forth reaction conditions which can be used with phenyl acetylene, methyl acetylene and diisopropenyl acetylene.

*Approximately 85% pure, the remainder being B 11 The boron-containing solid materials produced by practicing the method of this invention can be employed as ingredients of solid propellant compositions in accordance with general procedures which are well-understood in the art, inasmuch as the solids produced by practicing the present process are readily oxidized using conventional solid oxidizers, such as ammonium perchlorate, potassium perchlorate, sodium perchlorate, ammonium nitrate and the like. In formulating a solid propellant composition employing one of the materials produced in accordance with the present invention, generally from to 35 parts by weight of boron-containing material and from 65 to 90 parts by weight of oxidizer, such as ammonium perchlorate, are present in the final propellant composition. In the propellant, the oxidizer and the product of the present process are formulated in intimate admixture Wit-h each other, as by finely subdividing each of the materials separately and thereafter intimately admixing them. The purpose in doing this, as the art is aware, is to provide proper burning characteristics in the final propellant. In addition to the oxidizer and the oxidizable material, the final propellant can also contain an artificial resin, generally of the urea-formaldehyde or phenol-formaldehyde, type, the function of the resin being to give the propellant mechanical strength and at the same time improve its burning characteristics. Thus, in manufacturing a suitable propellant, proper proportions of finely divided oxidizer and finely divided boron-containing material can be admixed with -a high solids content solution of a partially condensed urea-formaldehyde or phenol-formaldehyde resin, the proportions being such that the amount of the resin is about 5 to 10 percent by weight, based upon the weight of the oxidizer and boron compound. The ingredients are thoroughly mixed with simultaneous removal of the solvent, and following this the solvent-free mixture is molded into the desired shape, as by extrusion. Thereafter, the resin can be cured by resorting to heating at moderate temperatures. For further information concerning the formulation of solid propellant compositions, reference is made to US. Patent No. 2,622,277 to Bonnell et al. and US. Patent No. 2,646,596 to Thomas et al.

It is claimed:

1. A method for the preparation of solid reaction products of pentaborane(1l) and an acetylene hydrocarbon which comprises reacting the pentaborane(11) and an acetylene hydrocarbon containing from 2 to 8 carbon atoms at a temperature of from about -25 C. to C., the molar proportion of acetylene hydrocarbon topentaborane(11) being within the range from about 0 .5 to 5.

2. The method of claim 1 wherein the acetylene hydrocarbon is isopropenyl acetylene.

3. The method of claim 1 wherein the acetylene hydrocarbon is divinyl acetylene.

No references cited.

TOBIAS E. LEVOW, Primary Examiner.

BENJAMIN R. PADGETT, Examiner.

L. A. SEBASTIAN, W. F. W. BELLAMY,

Assistant Examiners. 

1. A METHOD FOR THE PREPARATION OF SOLID REACTION PRODUCTS OF PENTABORANE (11) AND AN ACETYLENE HYDROCARBON WHICH COMPRISES REACTING THE PENTABORANE (11) AND AN ACETYLENE HYDROCARBON CONTANING FROM 2 TO 8 CARBON ATOMS AT A TEMPERATURE OF FROM ABOUT -25* C. TO 50* C., THE MOLAR PROPORTION OF ACETYLENE HYDROCARBON TO PENTABORANE (11) BEING WITHIN THE RANGE FROM ABOUT 0.5 TO
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